Pilger rolling mills



Oct. 3, 1967 H. H. FAHRENHOLZ 3,344,644 PILGER ROLLING MILLS 4Sheets-Sheet 1 Filed Sept. 29, 1964 Inventor- HE/NZ H. FAHEE l/HOLZ 1967H. H. FAHR ENHOLZ 3,344,644

PILGER ROLLING MILLS 4 Sheets-Sheet 3 Filed Sept. 29, 1964 lll mm t

Inventor: HE/NZ H. FAHEENHOLZ k A Mukn Och 1967 V H. H. FAHRENHOLZ3,344,644

PILGER ROLLING MILLS Filed Sept. 29, 1964 4 Sheets-Sheet 4 F ig.4

Inventor- United States Patent 3,344,644 PILGER ROLLING MILLS Heinz H.Fahrenholz, Monchen-Gladbach, Germany, assignor to Mannesmann-MeerAktiengesellschaft, Monchen-Gladbach, Germany, a corporation of GermanyFiled Sept. 29, 1964, Ser. No. 400,033 Claims priority, applicationGermany, Sept. 30, 1963, M 58,371 2 Claims. (Cl. 72-250) ABSTRACT OF THEDISCLOSURE A pilger rolling mill provided with means for rotation of therolled billet including a rotating cam disc and worm gearing wherein thedisc has at least two cam surfaces which extend away from the center ofrotation of the disc to different distances, and the disc is rotated bythe driving crank of the mill through reduction gears which have areduction ratio corresponding to the number of cam surfaces. The wear ofthe pass thereby is materially reduced.

This invention relates to pilger rolling mills, particularly pilgercold-rolling mills, of the kind in which the billet is rotated at astage in the rolling process through a worm and worm-wheel arrangementin which the worm is moved longitudinally to effect operation by a camfollower bearing on a rotating cam disc.

As a rule high-quality material is treated in tube making by the pilgerrolling process. It is therefore also necessary to select for thispurpose tools made of suitable highalloy material treated by specialprocesses. Since the tools thus treated, that is to say the roll jawsand the rolls (referred to hereinafter as a pass), are costly, therolling mill specialists and tube manufacturers have given a great dealof consideration to the manner in which the life of the pass can beincreased to such an extent as to contribute to the more economicutilization of the plant as a whole.

In addition to natural wear caused in the pass by the rolling processthere are other matters to be taken into account. As is sufficientlywell known, tube-wall thickening occurs on the billets in the region ofthe roll gap and this tube-wall thickening can be equalized again byrotating the billet through a certain angle during the subsequentstep-back movement. Since, in all known pilger mills, this angle isabout 60, it is only natural that wear on the pass, being always at thesame place, is particularly striking. Eroded places are produced, whichcan only be removed by subsequent machining and the consequentconsiderable loss of material so that the life of the pass is reduced.

The invention is concerned with the problem of controlling the rotationof the billet, so that the wear of the pass due to roll-gap thickeningwill be distributed over a larger angular range, and in addition, thedepth of the eroded places will be kept within acceptable limits.

In a pilger rolling mill according to the invention the cam disc has twoor more cam surfaces which extend away from the center of rotation ofthe disc to different distances and the disc is rotated from the drivingcrank of the rolling mill through reduction gearing having a reductionratio corresponding to the number of cam surfaces on the disc.

Preferably the cam disc is provided with at least three cam surfaces ofdifferent heights, rotation of the cam 'disc being adapted to theworking rhythm by the interposition of a reduction gearing with theratio of at least 3: 1.

So that the invention will be better understood it will be furtherdescribed by way of example with reference to the accompanying drawingsin which: 1

Patented Oct. 3, 1967 FIGURE 1 is a plan of a pilger cold-rolling millaccording to the invention;

FIGURE 2 is a diagram of the controlgearing of the mill shown in FIGURE1;

FIGURES 3A and 3B illustrate details of the device according to theinvention, the detail being that indicated at A in FIGURE 2;

FIGURE 4 shows, with reference to a pass represented in section, on theleft-hand side the wear heretofore produced by rotation of a billetthrough about 60, and on the right-hand side, the variation in wearaccording to the invention using three cams of different heights on thecam disc.

Referring now to the drawings, a roll stand 1 (FIG- URE 1) isreciprocated by means of connecting rods 2, crankshaft 3, coupling 4,gearing 5 and driving motor 6. Simultaneously with the reciprocation ofthe roll stand 1, a rotary movement of a pass 7 is produced by means ofstationary racks 8 on which pinions 9', on the pass axles mesh, a billet10 being thereby drawn to a finished tube on a mandrel 30. The necessaryfeed and rotary movements of the billet 10 are produced by a controlgearing 11, which is driven through a control shaft 12, rigidlyconnected to the gearing 5 by a bevel gear pair 13 and a coupling 14.

FIGURE 2 shows on the left how feed is effected by means of the controlshaft 12 through spur gears and bevel gears, while on the right,rotation of the billet is produced through bevel gearing and reductiongearing at point A.

In the rotating device (FIGURES 2, 3A and 3B) the control shaft 12drives a worm 18 through bevel gearing 15, transmission shaft 16 andspur gearing 17. A wormwheel 19 is connected to a rotating shaft 20leading to a clamping slide 27 having clamping jaws (FIGURE 1).

Through the control shaft 12, a reduction gearing 21 forms the drive fora cam disc 22, which by means of a roller'23 connected to the worm 18,moves the worm radially upward. Due to this upward movement of the worm18, the wormwheel 19 and hence the rotating shaft 20 are rotated througha certain angle. By means of the rotating shaft 20, the billet 10 willbe rotated in the clamping slide 27 by means of its extension, andrearwardly .a mandrel abutment 31 with mandrel rod 29 will be rotatedthrough the same angle as the billet 10. A helical compression spring 28or like means ensures firm application of the roller 23 on the tracksurface of the cam disc 22. As will be seen from the drawings by way ofexample, the rotary movement of the billet 10 will be operated throughthe rotating shaft 20, which is rotated through an angular range, themagnitude of which is determined by the upward movement of the worm 18caused by the individual different cams (a-b-c) (FIG- URE 3A) on the camdisc 22, the rotation process in regard to time being controlled throughthe reduction gearing 21 by the control shaft 12 off the crank mechanism5' of the rolling mill.

Return of the worm 18 is effected in a positive manner by its connectionwith the spur gearing 17 and bevel gearing 15, the wormwheel 19 formingthe fixed abutment and not rotating, due to its connection with theclamping slide 27, so that the worm 18 is screwed out of the latter.

Due to the introduction, according to the invention, of a cam dischaving two or more earns a, b, c, of different heights (FIGURE 3A)uniformly distributed over the circumference, in the rotating operationand corresponding reduction gearing, the rolling gap thickening of thetube or billet occurs at the same place in the pass only in the course,for example, of three complete revolutions, so that wear in the pass,due to tube thickening, is distributed over a larger angular range(u-B-y), FIGURE 4, whereby the depth of wear moves within the scope ofthe normal erosion by the rolling process, so that subsequent machiningoifers in the long run greater possibilities of re-utilization of theroll pass.

I claim:

1. In a pilger rolling mill including a reciprocating roll stand; a passconsisting of rollers and roll jaws disposed therein; a billet engagedin said pass; a drive shaft for rotating said billet, a control shaftconnected to said drive shaft; the improvements which comprise saiddrive shaft and control shaft being connected by means of gears, and acam disc interposed between said gears, said cam disc having at leasttwo carn surfaces extending away from the center of rotation of the discto distances which are different relative to each other; said disc beingconnected to said control shaft by a reduction gear having a 4 reductionratio corresponding to the number of cam surfaces on said disc.

2. The pilger rolling mill as defined in claim 1, wherein said cam disceffects periodic repetition of the angles of rotation of said cams.

References Cited UNITED STATES PATENTS Re. 13,377 3/1912 Blaxier 72252681,557 8/1901 Laybourne et a1 72252 2,021,686 11/1935 Gassen 724212,081,959 6/ 1937 Scoutten 72250 RICHARD J. HERBST, Primary Examiner.

H. D. HOINKES, Assistant Examiner.

1. IN A PILGER ROLLING MILL INCLUDING A RECIPROCATING ROLL STAND; A PASSCONSISTING OF ROLLERS AND ROLL JAWS DISPOSED THEREIN; A BILLER ENGAGEDIN SAID PASS; A DRIVE SHAFT FOR ROTATING SAID BILLET, A CONTROL SHAFTCONNECTED TO SAID DRIVE SHAFT; THE IMPROVEMENT WHICH COMPRISE SAID DRIVESHAFT AND CONTROL SHAFT BEING CONNECTED BY MEANS OF GEARS, AND A CAMDISC INTERPOSED BETWEEN SAID GEARS, SAID CAM DISC HAVING AT LEAST TWOCAM SURFACES EXTENDING AWAY FROM THE CENTER OF ROTATION OF THE DISC TODISTANCE WHICH ARE DIFFERENT RELATIVE TO EACH OTHER; SAID DISC BEINGCON-